Cellular Respiration Chapter 7

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Questions and Answers

During which phase of cellular respiration is the majority of ATP produced?

  • Pyruvate oxidation
  • Oxidative phosphorylation (correct)
  • Citric acid cycle (TCA)
  • Glycolysis

What is the primary role of the electron transport chain (ETC) in cellular respiration?

  • To generate a proton gradient for ATP synthesis. (correct)
  • To break down glucose into pyruvate.
  • To directly produce ATP by substrate-level phosphorylation.
  • To convert pyruvate into Acetyl-CoA.

Which of the following molecules serves as the final electron acceptor in the electron transport chain?

  • Oxygen ($O_2$) (correct)
  • NADH
  • FADH2
  • ATP synthase

What is the direct energy source that drives ATP synthesis by ATP synthase during chemiosmosis?

<p>The proton gradient across the inner mitochondrial membrane. (D)</p> Signup and view all the answers

Which of the following is a mobile electron carrier that transports electrons between protein complexes in the electron transport chain?

<p>Ubiquinone (CoQ) (A)</p> Signup and view all the answers

What type of gradient is generated by the electron transport chain, which is crucial for chemiosmosis?

<p>Proton gradient (C)</p> Signup and view all the answers

Which protein complex in the electron transport chain (ETC) receives electrons directly from FADH2?

<p>Complex II (D)</p> Signup and view all the answers

Why is the ATP yield from FADH2 less than that from NADH in the electron transport chain?

<p>FADH2 enters the ETC at a later complex, bypassing an earlier proton pump. (B)</p> Signup and view all the answers

Where does the electron transport chain get the electrons it uses to facilitate ATP production?

<p>From the oxidation of NADH and FADH2. (D)</p> Signup and view all the answers

What is the primary function of ATP synthase?

<p>To catalyze the synthesis of ATP from ADP and inorganic phosphate. (C)</p> Signup and view all the answers

What is the approximate efficiency of cellular respiration in extracting energy from glucose?

<p>34% (A)</p> Signup and view all the answers

In the absence of oxygen, some cells can still produce ATP via anaerobic respiration. What is the final electron acceptor in this process?

<p>Pyruvate or a derivative of pyruvate (D)</p> Signup and view all the answers

During electron transport, what directly facilitates the movement of protons from the mitochondrial matrix to the intermembrane space?

<p>The protein complexes of the electron transport chain. (B)</p> Signup and view all the answers

What is the role of the 'shuttle systems' in the context of ATP yield from cellular respiration?

<p>They facilitate the movement of electrons from cytosolic NADH into the mitochondria. (A)</p> Signup and view all the answers

Why is the net ATP yield from cellular respiration typically lower than the theoretical maximum?

<p>All of the above (D)</p> Signup and view all the answers

What distinguishes Complex IV from other complexes in the electron transport chain?

<p>It transfers electrons to oxygen, forming water. (A)</p> Signup and view all the answers

Which of the following is the correct sequence of electron carriers in the electron transport chain?

<p>Complex I → CoQ → Complex III → Cytochrome c → Complex IV (C)</p> Signup and view all the answers

Which of these is NOT a component of ATP synthase?

<p>A matrix porin to regulate ion flow (C)</p> Signup and view all the answers

If a drug inhibited the function of ubiquinone (CoQ), what would be the most likely direct consequence?

<p>Decreased proton pumping into the intermembrane space (C)</p> Signup and view all the answers

In cellular respiration, after the electron transport chain has created a proton gradient, what is the next DIRECT step in ATP production?

<p>Protons flow down their concentration gradient through ATP synthase (B)</p> Signup and view all the answers

How does the chemical synthesis of ATP relate to the proton electrochemical gradient in chemiosmosis?

<p>The gradient's energy is harnessed to drive ATP synthase to bind ADP and Pi together (C)</p> Signup and view all the answers

Why can't NADH simply diffuse through the mitochondrial membrane to deliver its electrons to the electron transport chain?

<p>The mitochondrial membrane is impermeable to NADH, requiring specific shuttle systems. (D)</p> Signup and view all the answers

Suppose a mutation disabled ATP synthase. What immediate effect would this have on the electron transport chain?

<p>The ETC would slow down because the proton gradient would become too high. (D)</p> Signup and view all the answers

Considering that cellular respiration harnesses ~34% of glucose's potential energy, where does the remaining percentage of energy go?

<p>It's lost primarily as heat. (A)</p> Signup and view all the answers

How does the process of chemiosmosis directly contribute to ATP synthesis?

<p>By providing the energy needed for ATP synthase to bind ADP and inorganic phosphate. (A)</p> Signup and view all the answers

Flashcards

Electron Transport Chain (ETC)

A series of protein complexes embedded in the mitochondrial inner membrane that transfers electrons from electron carriers.

Proton Motive Force (PMF)

The force generated by the ETC that pumps protons across the inner mitochondrial membrane.

Chemiosmosis

An energy coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP.

ATP Synthase

An enzyme complex that harnesses the proton gradient to produce ATP.

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Glycolysis

The initial step in glucose breakdown, occurring in the cytoplasm, breaking glucose into two molecules of pyruvate.

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Pyruvate Oxidation

The process where pyruvate is converted to Acetyl-CoA, linking glycolysis to the citric acid cycle.

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Citric Acid Cycle (TCA)

A series of reactions that extract energy from acetyl CoA, producing ATP, NADH, and FADHâ‚‚.

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Oxidative Phosphorylation

Process where ATP is generated using the energy released by the electron transport chain and chemiosmosis.

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Oxidative-phosphorylation

The process where ATP production is directly linked to the electron transport chain.

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Mobile Electron Carriers

Mobile carriers that transport electrons between protein complexes in the electron transport chain.

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Ubiquinone (CoQ)

A lipid-soluble electron carrier that transports electrons between protein complexes I/II and III in the ETC.

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Cytochrome C

Transports electrons between Complex III and IV.

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NADH ATP yield

NADH yields how much ATP?

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FADHâ‚‚ ATP yield

FADHâ‚‚ yields how much ATP?

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Shuttle Systems

They transfer electrons from the cytosol to the mitochondrial matrix.

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Final electron acceptor

What is the final electron acceptor in the electron transport chain?

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ETC location

What part of the Mitochondria does the ETC take place in?

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Complex I

It consists of flavoprotein combined with an iron-sulfur (Fe-S) protein.

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Complex II

It consists of FAD combined with a Fe-S protein.

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Complex IV

It consists of cytochrome a combined with cytochrome a3.

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Study Notes

  • Cellular respiration consists of harvesting chemical energy
  • Chapter 7 (pp.154-160) covers the topic of Cellular respiration

Overview

  • Electron Transport Chain(ETC) is a key part of cellular respiration
  • ETC generates proton motive force (PMF)
  • Chemiosmosis is a process involved in cellular respiration
  • ATP Synthase is an enzyme that creates ATP
  • ATP yield is from a proton gradient
  • Shuttle systems also impact ATP yield
  • Net ATP yield is a measure of cellular respiration efficiency
  • The effectiveness of cellular respiration in extracting energy from glucose can be calculated

Phases of Cellular Respiration

  • Cellular respiration occurs in three metabolic phases:
  • Glycolysis is the first phase
  • Pyruvate oxidation and the Citric acid cycle (TCA) is the second
  • Oxidative phosphorylation is the third

Electron Transport Chain

  • The ETC allows for ATP production through oxidative phosphorylation

Electron Transport Chain (ETC) Components

  • ETC consists of a protein complex embedded in the mitochondrial inner membrane and mobile electron carriers
  • ETC receives electrons from electron carriers like NADH
  • Transferred electrons between the ETC components are in reduced/oxidized states
  • Oâ‚‚ acts as the final electron receiver
  • Electrons lose free energy with each transfer to build a proton gradient over the mitochondrial inner membrane

Components of the ETC

  • Protein complexes exist of:
  • Complex I (flavoprotein combined with an iron-sulfur (Fe∙S) protein)
  • Complex II (FAD combined with a Fe∙S protein)
  • Complex III (cytochrome b combined with a Fe-S protein and cytochrome c1)
  • Complex IV (cytochrome a combined with cytochrome a3)
  • Mobile electron carriers include:
  • Ubiquinone/Coenzyme Q (CoQ) which transports electrons between Complex I and III or II and III
  • Cytochrome c which transports electrons between Complex III and IV

Sequencing of ETK components

  • Complex I
  • Ubiquinone (CoQ)
  • Complex II
  • Complex III
  • Cytochrome c
  • Complex IV
  • Oâ‚‚ is the final e- acceptor in the Mitochondrial Matrix

Free Energy

  • This decreases during electron transfer

ETC Generates Proton-Motive Force

  • Released energy during transfer is used to actively pump protons from the mitochondrial matrix to the intermembrane space
  • A proton gradient is generated across the membrane, creating a chemical and electrical gradient
  • This gradient represents stored (potential) energy called proton-motive force (PMF)

Chemiosmosis

  • The chemical synthesis of ATP is because of proton gradient over the mitochondrial inner membrane
  • The potential energy, stored as a proton gradient (PMF), is used by ATP synthase to produce ATP
  • ATP synthase is an integral protein found in the inner mitochondrial membrane

ATP Synthase

  • Consists of several parts
  • Functions like an active ion-transport pump
  • Instead of using ATP to pump against a gradient, the natural proton gradient is used to generate ATP

ATP Production

  • Research shows the amount of ATP generated per electron carrier
  • 1 NADH producing 2.5 ATP
  • 1 FADHâ‚‚ producing 1.5 ATP
  • Electrons from NADH and FADH2 are transmitted differently by ETC systems
  • The proton gradient is also used for other purposes, like the transport of pyruvate from the cytosol to the matrix

ATP Production: Shuttle Systems

  • Electrons generated from glycolysis, carried by NADH, are transported to the mitochondrial matrix
  • NADH cannot move across the mitochondrial membrane
  • Shuttle systems transfer electrons from the cytoplasm to the mitochondrial matrix
  • In heart, liver, and kidneys, electrons are transferred from glycolysis to NADH within the mitochondrion
  • In skeletal muscle and brain, electrons are transferred from glycolysis to FADH within the mitochondrion.

ATP Yield

  • Tissue-dependent commuting system used for transport of electrons from the membrane:
  • Heart, liver, kidney yields between 30-32 ATP
  • Skeletal muscle, brain yields between 30-32 ATP

Net ATP Production

  • Glycolysis produces 2 ATP and 2 NADH
  • Pyruvate oxidation produces 2 NADH and 2 COâ‚‚
  • The citric acid cycle produces 2 ATP, 6 NADH, and 4 COâ‚‚
  • Oxidative phosphorylation produces 25 ATP from NADH and 3 ATP from FADHâ‚‚

Effectiveness of Cellular Respiration

  • Hydrolysis of one ATP molecule produces -30.5 kJ/mol under standard conditions
  • Cellular respiration produces 32x(-30.5) = -976 kJ/mol also under standard conditions
  • The potential energy content of chemical bonds in one glucose molecule is -2870 kJ/mol
  • Cellular respiration harnesses ~34% of glucose's potential chemical energy
  • Car's internal combustion engine utilizes ~25% of energy in gasoline

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